Wednesday. I so want to be done with the apartment hunting. Last night was a disappointment--a beautiful house on Glückstraße, but not enough privacy.
1109.1821
The CFHTLS-Strong lensing legacy survey (SL2S): investigating the group-scale lenses with the SARCS sample
More, Cabanac, More, Alard, Limousin, Kneib, Gavazzi, Motta
Use of semi-automatic method to find gravitational arcs, visual inspection-pruned. 54 systems, 12 giant arcs, 2 radial arcs. Sytematic alignment of giant arcs with the ellipticity of the baryonic component of the lens. Lens redshift distribution of arcs (estimated from photometry) peaks at z~0.5. Largest lens sample probing group-scales for the first time. Compare observed image separation distribution with theoretical models: ISD accommodate models with both with and without adiabatic contraction (probably need more samples, yah?). (indeed,) Large sample might constrain relations such as the concentration-mass relation, mass-luminosity relation and slope of the luminosity function.
1109.1828
The XMM Cluster Survey: predicted overlap with the Planck Cluster Catalogue
Viana, da Silva, Ramos, Liddle, Lloyd-Davies, Romer, Kay, Collins, Hilton, Hosmer, Hoyle, Mehrtens, Miller, Sahlan, Stanford, Stott
Present serendipitously-discovered 15 clusters of galaxies in XCS that have high detection probability by Planck (3 of which already appear in the Planck Early SZ (ESZ) catalogue. Detection probability calculated from flat LCDM (WMAP7) with XCS selection function and Planck sensitivity; covariance of the cluster X-ray luminosity, temperature, and integrated comptonization parameter (?), as a function of cluster mass and redshift, as found in Millenium Gas Simulations. Also: characterize properties of the galaxy clusters in the final data release of XCS that are expected to be detected by Planck extended mission. Briefly discuss possible joint applications of the XCS and Planck data.
1109.1838
The pussling assembly of the MW halo -- contributions from dwarf Spheroidals and globular clusters
Koch, Lapine, A?l?kan
Classification of star clusters, low-luminosity galaxies, or tidal overdensities remain unclear for the MW satellites. Likewise, contribution to the build-up of the halo is still debated. Discuss current knowledge of stellar populations and chimo-dynamics in these faint satellites, with focus on dwarf spheroidal galaxies and the globular clusters in the outer Galacitic halo. Whether some of the outermost halo objects are dynamically associated with the MW halo at all is addressed, in terms of Leo I and II dwarf galaxies.
* I wish they could tell the conclusions...
1109.1846
Testing Einstein gravity with cosmic growth and expansion
Zhao, Li, Linder, Koyama, Bacon, Zhang
* Pade approximant: "best" approximation of a function by a rational function of given order. With this technique, the approximant's power series agrees with the power series of the function it is approximating. Often gives better approximation of the function than truncating its Taylor series. May still work where the Taylor series do not converge. Used extensively in computer calculations.
Test Einstein gravity using cosmological observations of both expansion and structure growth, with data from Union 2.1 (SNeIa), WMAP7 (CMB), CFHTLS (WL), and SDSS DR7 (z-space distortion). Fid modified gravity parameters of the generalized Poisson equations simultaneously with the effective equation of state ("w") for the BG evolution, exploring the covariances and model dependence. Results: GR is a good fit to the combined data. Using Pade approximant form for gravity deviations accurately captures the time and scale dependence for theories like f(R) and DGP gravity, weights high ad low redshift probes fairly.
1109.1888
Distribution function approach to redshift space distortions
Seljak, McDonald
Develop phase space distribution function approach to RSD: z-space density can be written as a sum over velocity moments of the distribution function. Moments are density weighted; the lowest orders are density, momentum density and stress-energy density. The series expansion is convergent on large scales. Expand velocity moments into helicity modes: Eigenmodes under rotation around the axis of Fourier mode direction; generalizes the scalar, vector, tensor decomposition of perturbations to an arbitrary order. Only equal helicity moments correlate; derive the angular dependence of the individual contributions to the redshift space power spectrum in terms of angle mu between k and LOS. Dominant term of mu^2 dependence on large scales is the X-correlation between the density and scalar part of momentum density, which can be related to the time derivative of the matter power spectrum. Additional terms contributing and dominating on small scales are the vector part of momentum density-momentum density correlations, the energy density-density correlations, and the scalar poart of anisotropic stress density-density correlations. Identify 7 terms contributing to mu^4 dependence. Some of the advantages of the distribution function approach are: the series expansion converges on large scales and remains valid in multi-stream situations. Brief discussion of implications for RSD in galaxies relative to DM, highlighting the issue of scale dependent bias of velocity moments correlators.
1109.1981
The complementarity of z-space distortions and the ISW effect
Shapiro, Crittenden, Percival
* RSD and ISW give orthogonal info
Assuming GR is correct on large-scales, RSDs and the ISW effect are both sensitive to the time derivative of the linear growth function. Investigate complementary or redundant information when combined to constrain evolution of the linear velocity power spectrum (f(z)/sigma8(z)), where f(z) is the logarithmic derivative of sigma8 wrt (1+z). Using 3d spherical harmonic expansion, compute covariance matricies of the signals for galaxy survey + CMB (Planck-like). Spherical harmonic basis allows accurate ISW estimates by avoiding the plane-parallel approximation (?); retains RSD information that is otherwise lost when projecting angular clustering onto redshift shells. Find correlation between ISW and RSD signals are low since the probes are sensitive to different modes. For default surveys, on large scales (k<0.05 Mpc/h) the ISW can improve constraints on f\sigma_8 by more than 10% compared to using RSD alone. In the future, when precision RSD measurements are available on smaller scales, the constraints from ISW will not be competitive, but will remain a useful consistency test for possible systematic contamination and alternative models of gravity.
* RSD and ISW both probe derivatives of linear growth; ISW sensitive to photons that come out of potential well (which might change shape over time) and is sensitive on large scales; RSD probes the peculiar velocity of galaxies falling into the potential well, and is sensitive on small scales.
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